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In my experience, (I have GRENADED 4, 7.5" rears. one behind a 4.2L V8, and the others behind stock 5.0L's) It is the spider gears and the main carrier caps that let go. The last one I wrecked, I never did find all the pieces of the spider gears, and the caps both broke into 3 seperate pieces EACH. spend your money wisely. go 8.8" or waste your money and blow up a 7.5

A properly built 7.5" rear will withstand quite a bit of abuse. The key is to get a rear end girdle cover (yes, they exist for 7.5" rears) and a good locking center section. After that, thrash away.

So the weight thing...let me explain. I pulled the 80 lb. difference info from two different sources: my mechanic, and a magazine article. The mag--meh, not so sure about them as they've had errors in the past, but still, it felt correct to me. My mechanic--very trustworthy as he's the driveline specialist at the Ford dealership where he works. I think since he works on FWD and RWD vehicles, Focuses to F-350's, and also races Mustangs on the weekends, he can give a very good idea of weight differences between components.

A standard Cougar/T-Bird 7.5" open rear end with 2.73 gears and 9" drum brakes is the baseline. The top-of-the-line, I suppose, would be a 1987-88 Turbo Coupe 8.8" locking rear end with 3.73 gears, 10" discs and quad shock brackets. Fully loaded with brakes and gear oil, the difference in weight between those two rear ends is quite dramatic. Is it exactly 80 lbs.? Never said that. Is it realistically more like 40-50 lbs.? Possibly. I do know that I can carry a basic, loaded 7.5" rear around by myself but need help with a loaded 8.8" rear. And I'm not that big of a pu$$y...I can lift some fairly serious weight around. So it the real difference between 7.5" and 8.8" rear ends a mere 10 lbs.? I don't think so. Bare, possibly. Not fully loaded. No way. I think it's funny how everyone jumps to conclusions about "only a 10 lb. difference" when there aren't even any brakes attached. Isn't that how you, um, you know...USE a rear end in the real world?!

In the near future I will have the opportunity to weigh both, fully loaded to fully loaded, and will report actual numbers when I get them. I also have separate components (gears, center sections, 9" and 10" drums, etc.) that I'll throw into the mix, just for solid numbers. That should help smooth things out.

buddy of mine had a Dominator Mustang that had a 7.5 under it-withstood a bunch of high-13 second 1/4 runs...
I pulled my TC's 8.8 just last week, and I will say that there IS more than 10 pounds of weight difference between it and a 7.5, and this was the complete rear, even the quad shocks
I could barely lift it into the back of my truck, and I ain't no wimp!
I can pack around a 7.5 by myself, but I sure as hell can't an 8.8..

I believe that the 8.8 axle tubes are only marginally larger as well. I changed the 7.5 trac-loc in my 86' for a 90' Lincoln 8.8 trac-loc w/rear discs and didn't notice much of a weight difference with the exception that I had left in the stock gears. BIG mistake!! I have since pulled the 8.8 and swapped in a 03' Cobra IRS. Now that does weigh 80# more than even the 8.8 live axle. But the trade off is worth it for me as I too will be autocross/road racing my car

Some Rangers came with 7.5's some came with 8.8's. TC rears will not bolt into a Ranger - the Ranger has leaf springs (and brackets necessary to install them), while the TC rear is setup for four link/coil spring (again, with brackets to install 'em)